(a) Field of the Invention
The present invention relates to an organic light emitting device.
(b) Description of the Related Art
The organic light emitting device includes an organic light emitting element and a plurality of thin film transistors to drive it. The thin film transistors are made of a plurality of thin films and are generally disposed at the lower side of the organic light emitting device, the organic light emitting element is disposed at the upper side thereof, and an anode of the organic light emitting element is disposed at the lower side and a cathode thereof is disposed at the upper side.
The organic light emitting device may be divided into a top emission type that emits light to the upper side and a bottom emission type that emits light to the lower side. In the case of the bottom emission type, the thin film transistors are disposed under the organic light emitting element such that the area where the light is emitted is decreased, and accordingly it is advantageous to apply the top emission type with regard to the aperture ratio. Also, in the bottom emission type, spots may be generated due to optical interference generated when the light passes through the thin films, but the thin films exist in a minor amount on the path where the light passes such that the possibility thereof is slim.
In the case of the top emission type, since there is no transparent material satisfying the work function condition required as the cathode, an opaque metal material is very thinly deposited to be used as the cathode, thereby allowing the light to pass. However, resistance of the cathode is increased in this case such that an additional common voltage line for transmitting a common voltage on a substrate is needed, and the cathode of the organic light emitting element is connected to the common voltage line.
However, when the common voltage line is formed separately from the cathode, an emitting member between the cathode and the common voltage line must be removed such that the manufacturing process becomes complicated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.